Process for the synthesis of O-desmethylvenlafaxine

ABSTRACT

Provided are processes and intermediates for the synthesis of O-desmethylvenlafaxine.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims the benefit of the following U.S. Provisional Patent Application Nos. 60/833,616, filed Jul. 26, 2006; 60/837,879, filed Aug. 14, 2006; 60/849,216, filed Oct. 3, 2006; 60/843,998, filed Sep. 11, 2006; 60/849,255, filed Oct. 3, 2006; 60/906,639, filed Mar. 12, 2007; and 60/906,879, filed Mar. 13, 2007. The contents of these applications are incorporated herein by reference.

FIELD OF THE INVENTION

The invention encompasses a process for the synthesis of O-desmethylvenlafaxine.

BACKGROUND OF THE INVENTION

Venlafaxine, (±)-1-[2-(Dimethylamino)-1-(4-methoxyphenyl)ethyl]cyclohexanol, of the following formula,

is the first of a class of anti-depressants. Venlafaxine acts by inhibiting re-uptake of norepinephrine and serotonin, and is an alternative to the tricyclic anti-depressants and selective re-uptake inhibitors.

O-desmethylvenlafaxine, 4-[2-(dimethylamino)-1-(1-hydroxycyclohexyl)ethyl]phenol, of the following formula,

is reported to be a metabolite of venlafaxine, which is known also as an inhibitor of norepiniphrine and serotonin uptake, See Klamerus, K. J. et al., “Introduction of the Composite Parameter to the Pharmacokinetics of Venlafaxine and its Active O-Desmethyl Metabolite,” and J. Clin. Pharmacol. 32:716-724 (1992).

Processes for the synthesis of O-desmethylvenlafaxine by demethylation of the methoxy group of venlafaxine are described in U.S. Pat. Nos. 7,026,508 and in 6,689,912.

The synthesis disclosed in the above patents is performed according to the following scheme:

wherein “MBC” refers to methyl benzyl cyanide, “CMBC” refers to cyclohexyl methylbenzyl cyanide, “DDMV” refers to didesmethyl venlafaxine, and “ODV” refers to O-desmethylvenlafaxine.

The demethylation process disclosed in U.S. Pat. No. 7,026,508 provides ODV succinate salt by using L-selectride, which is an alkali metal salt of trialkyl borohydride; where hydrogen gas is formed during the reaction. Hence, the process isn't suitable for industrial scale manufacture.

US application No. 2005/0197392 describes a method for preparing (±)O-desmethylvenlafaxine hydrochloride salt by reacting venlafaxine with lithium diphenyl phosphide.

U.S. Pat. No. 6,689,912 describes demethylation process performed by using a salt of high molecular weight alkane, arene, or arylalkyl thiolate anion in the presence of protic or aprotic solvent. The salt can be prepared separately and then react with venlafaxine, or can react in-situ with venlafaxine. When prepared separately, the solvent, methanol should be removed. This operation is very complicated because the mixture containing the salt is highly viscous, hence the operation necessitate long time even under high vacuum. When the reaction is performed in-situ via removal of methanol in situ, this operation is still tedious and only partially successful, since it is difficult to reach the high temperature that the reaction necessitate to advance.

The described ODV synthesis processes are all indirect, i.e; performed via Venlafaxine. The present invention provides a direct synthesis of O-desmethylvenlafaxine; i.e.; without passing through venlafaxine as an intermediate.

SUMMARY OF THE INVENTION

In one embodiment, the invention encompasses hydroxyphenyl dimethylamide (OBA), having the following formula,

In another embodiment, the present invention provides a process for preparing hydroxyphenyl dimethylamide (OBA) comprising combining hydroxybenzyl carboxy (OBCarboxy), a catalyst and an acid activating agent to obtain an activated acid; recovering the activated acid, and combining it with a dimethylamine to obtain OBA.

Preferably, the process for preparing OBA is done in the presence of an organic solvent.

In yet another embodiment, the present invention provides a process for preparing ODV by preparing OBA as described above, and converting it to ODV. OBA can be transformed to ODV via another intermediated such as COBA.

In yet another embodiment, the present invention encompasses hydroxy protected OBA (POBA), having the following formula,

In another embodiment, the present invention encompasses a process for preparing POBA comprising; combining OBA with a hydroxyl protecting agent and a base.

In yet another embodiment, the present invention provides a process for preparing ODV by preparing POBA as described above, and converting it to ODV. POBA can be transformed to ODV via another intermediated such as PCOBA.

In yet another embodiment, the present invention encompasses cyclohexylOBA (COBA), having the following formula,

In one embodiment the process for the preparation of cyclohexylOBA (COBA) comprising: reacting OBA with cyclohexanone and a base able to form a carbanion; and recovering the obtained COBA.

In yet another embodiment, the present invention provides a process for preparing ODV by preparing COBA as described above, and converting it to ODV, by any method known in the art, i.e: the method described above.

In yet another embodiment, the present invention encompasses a hydroxyl protected COBA (PCOBA), having the following formula,

PCOBA

In another embodiment the process for preparing PCOBA comprising; combining POBA with cyclohexanone and a base able to form a carbanion; and recovering the obtained PCOBA.

In yet another embodiment, the present invention provides a process for preparing ODV by preparing PCOBA as described above and converting it to ODV, by any method known in the art, i.e: the method described above.

In another embodiment, the present invention encompasses a process for preparing ODV from COBA comprising: reacting COBA and a reducing agent to obtain ODV, where optionally, PCOBA can be used as a starting material.

In another embodiment, the present invention encompasses a process for preparing ODV comprising the steps of: combining OBCarboxy, a catalyst and an acid activating agent to obtain an activated acid; recovering the activated acid and combining it with an amine to obtain OBA; reacting the obtained OBA with cyclohexanone and a base able to form a carbanion; recovering the obtained COBA and reacting the obtained COBA; a reducing agent; and recovering the obtained ODV, wherein, optionally, a protected derivative of OBA (POBA) can be used as a starting material and PCOBA is obtained, which is then reacted with the reducing agent to obtain ODV.

DETAILED DESCRIPTION OF THE INVENTION

As used herein, the term “ambient temperature” refers to a temperature of about 18° C. to about 25° C.

As used herein, the term “OBA” refers to hydroxyphenyl dimethylamide (IUPAC name 2-(4-hydroxyphenyl)-N,N-dimethylacetamide) of the following structure:

As used herein, the term “POBA” refers to protected hydroxyphenyl dimethylamide (IUPAC name: protected 2-(4-hydroxyphenyl)-N,N-dimethylacetamide) of the following structure:

wherein x is a hydroxy protecting group.

As used herein, the term “COBA” refers to cyclohexyl hydroxyphenyl dimethylamide (IUPAC name 2-(1-hydroxycyclohexyl)-2-(4-hydroxyphenyl)-N,N-dimethylacetamide) of the following structure;

As used herein, the term “PCOBA” refers to protected cyclohexyl hydroxyphenyl dimethylamide (IUPAC name: protected: 2-(1-hydroxycyclohexyl)-2-(4-hydroxyphenyl)-N,N-dimethylacetamide) of the following structure;

wherein x is a hydroxy protecting group.

As used herein, the term “ODV” refers to O-desmethylvenlafaxine.

The present invention provides a direct synthesis of ODV via novel intermediates. This process produces ODV and its intermediates in high yields and purity. In the process of the present invention ODV is synthesized without going through venlafaxine, leading to elimination of a demethylation step.

In the process of the invention, the intermediate OBA is condensed with cyclohexanone to form the intermediate COBA. Further, the carboxylic group of COBA is reduced, and the reduced product is converted to ODV. The process can be performed via the protected intermediates POBA and PCOBA, in order to increase the yield, due to avoidance of side-reactions. The process is described in the following scheme.

In one embodiment, the invention encompasses hydroxyphenyl dimethylamide (OBA) (IUPAC name 2-(4-hydroxyphenyl)-N,N-dimethylacetamide). OBA is characterized by ¹HNMR (Bruker DPX-300 (DMSO-d6)) with δ: 2.80 (s, CH₃—N), 2.96 (s, CH₃N), 3.53 (s, CH₂), 6.70 (m, H atom), 6.98 (m, H atom), 9.24 (s, OH). OBA has a mass of 180 (MS (CI+)=180).

In one embodiment the present invention provides isolated or purified OBA. Isolated refers to being separated from the reaction mixture in which it forms. Preferably the OBA is at least about 50% pure as measured by HPLC.

OBA is prepared by a process comprising combining hydroxybenzyl carboxy OBCarboxy (IUPAC name: (4-hydroxyphenyl)acetic acid)) catalyst and an acid activating agent to obtain an activated acid; recovering the activated acid, and combining it with an amine to obtain OBA.

Preferably, the catalyst is an organic catalyst. Most preferably, the catalyst is dimethyl formamide DMF or Pyridinium p-toluene sulfonate (PPTS). Typically, the reaction is done in the presence of a solvent. The solvent is an organic solvent that does not react with the acid activating agent. More preferably, the solvent is selected from a group consisting of C₆₋₁₂ aromatic hydrocarbon, preferably C₆ to C₈, a C₁₋₄ halogenated hydrocarbon, preferably chloroform, dichloromethane, a C₄₋₈ ether preferably C₄ to C₆ ether, more preferably tetrahydrofuran, diethylether, methyltert-butyl ether and mixtures thereof. Even more preferably, the solvent is selected from a group consisting of toluene, CH₂Cl₂ and THF. Most preferably, the solvent is CH₂Cl₂.

Usually, the reaction with the acid activating agent is exothermic; hence the mixture is cooled prior to combining it with the acid activating agent. Preferably, the mixture is cooled to a temperature of about −10° C. to about 10° C., preferably −5° C. to about 5° C., more preferably, to a temperature of about 0° C.

In order to decrease the exothermic effect of the reaction, the acid activating agent is added dropwise, preferably during 30 minutes to about 3 hours. Preferably, the acid activating agent is an agent that activates carboxylic acids, i.e., converts the “OH” to a suitable leaving group. The activating agent may be SOCl₂, COCl₂, DCC (N′-dicyclohexyl carbodiimide) or analogs, HOBT (N-Hydroxybenzotriazole), FMOC (fluorenylmethoxycarbonyl) or analogs (and other analogs used in peptide chemistry) or PC15 or (COCl)₂. Most preferably, the activating agent is SOCl₂.

Following to the addition of the activating agent, the obtained mixture is heated, preferably to a temperature of about 0° C. to about 30° C., preferably about 15° C. to about 28°. More preferably the heating is to a temperature of about ambient temperature.

The heated mixture is stirred for a sufficient time to obtain the activated acid, preferably for a period of time of about 0.5 to about 3 hours, preferably for about 1 to about 2.5 hours. More preferably, the stirring is for about 2 hours.

The activated acid is optionally recovered by any method known in the art. Preferably, it is recovered by removing the solvent and providing a residue comprising of the activated acid. One of ordinary skill of art can also devise a one pot process which skips recovery of the intermediate in the synthetic scheme.

Preferably the solvent is removed by evaporation under reduced pressure (pressure of below one atmosphere).

Then, the residue is optionally dissolved in another organic solvent; wherein the solvent is described above. Subsequently, the solution is combined with dimethylamine to provide a mixture. This reaction is more facile if a dimethylamine salt is used, and then the salt is removed with another amine. Preferably the amine salt is dimethylamine-HCl and the second amine is a C₃-C₉ trialkylamine, where each alkyl chain is independently selected from C₁-C₇ carbons. Example of such amine includes diisopropylethylamine. A gaseous amine can also be used. Preferably, the second amine is added dropwise, more preferably, during about 1 hour.

The mixture is then stirred for a sufficient time to obtain OBA. Preferably, the stirring is done over a period of time of about 1 hour to about 24 hours more preferably about 4 hours to about 16 hours. More preferably, the stirring is performed overnight.

OBA can be recovered. The recovery is preferably done by quenching the new mixture providing a precipitate; washing, filtering, and drying. Preferably, the quenching is done by adding a saturated solution of a base. More preferably, the base is an inorganic base, such as an alkali metal or alkaline earth metal carbonate/bicarbonate. Most preferably, the base is NaHCO₃.

Preferably, the precipitate is filtered under a reduced pressure. Preferably, the washing is done with methylene chloride, and the drying, under vacuum (pressure of less than about 100 mmHg). Preferably, the drying is at a temperature of about 20° C. to about 80° C. More preferably, the drying is done at room temperature.

The process for preparing OBA can further comprise a process for converting OBA to ODV. OBA can be transformed to ODV via another intermediated such as COBA.

In another embodiment, the present invention encompasses hydroxy protected OBA (POBA). Suitable hydroxy protected groups are listed in T. W. Greene, Protective Groups in Organic Synthesis, (2^(nd) ed.), which is incorporated herein by reference. Most preferably, POBA is a silyl-protected POBA, such as a tri(C₁₋₆ alkyl)silyl-protected POBA, wherein the alkyl groups can be the same or different, preferably t-butyldimethylsilyl ether (TBDMS)-protected OBA, or trimethylsilyl (TMS), with TBDMS being preferred, or DHP-protected OBA.

In one embodiment the present invention provides isolated or purified POBA, including TBDMS-OBA. Isolated refers to being separated from the reaction mixture in which it forms. Preferably the POBA is at least about 50% pure as measured by HPLC.

TBDMS-OBA is characterized by ¹HNMR (Bruker DPX-300 (DMSO-d6)) with δ: 0.20 (s, Me2Si), 0.99 (s, tBuSi), 2.85 (s, CH₃—N), 2.99 (s, CH₃N), 3.62 (s, CH₂), 6.77 (m, H atom), 7.10 (m, H atom).

POBA, including TBDMS-OBA, can be prepared by combining OBA with a suitable hydroxyl protecting agent and a base. An acid may also be used instead of a base.

Usually, the reaction is done in the presence of a solvent. Preferably, the solvent is an organic solvent. Preferably the solvent is a non-protic solvent. The organic solvent can be a C₆ to C₁₂ aromatic hydrocarbon or a C₁-C₆ chlorinated hydrocarbon or C₄₋₆ ether. More preferably, the solvent is selected from the group consisting of toluene, CH₂Cl₂ and THF. Most preferably, the solvent is CH₂Cl₂.

Preferably, the hydroxyl protecting agent is a trialkylsilyl halide, preferably a tri(C₁₋₆ alkyl)silyl halide, wherein the alkyl may be the same or different, preferably the trialkylsilyl halide is a trimethylsilyl halide or a tert-butyldimethylsilyl halide, wherein the halide is chloride or bromide or DHP (dihydropyran). Preferably, the hydroxyl protecting agent is a silyl protecting group or DHP (dihydropyran). More preferably, the hydroxyl protecting agent is TBDMS-Cl, acetylchloride or acetic anhydride.

Preferably, the base is imidazole. Other bases such as pyridine, triethylamine, lutidine, dimethylaminopyridine may also be used.

The obtained combination is stirred at a temperature of about 0° C. to about 100° C., preferably about 40° C. to about 70° C. Preferably, the stirring is done at a temperature of about 55° C.

Preferably the above combination is maintained, while stirring, for about 0.5 hour to about 24 hours, preferably about 1 hour to about 4 hours, more preferably for about two hours, during which POBA is formed.

The process for preparing POBA can further comprise a recovery process. The recovery is, preferably done by quenching the combination providing a two-phase system; separating the obtained two phases, washing and drying the organic phase, followed by filtering and solvent evaporation under reduced pressure (pressure of less than one atmosphere). Preferably, the combination is quenched with brine and 10% aqueous solution of citric acid.

The process for preparing POBA can further comprise a process for converting POBA to ODV. POBA can be converted to ODV via COBA or PCOBA.

In another embodiment, the present invention encompasses cyclohexylOBA (COBA). Also provided is isolated or purified COBA. Isolated refers to being separated from the reaction mixture in which it forms. Preferably the COBA is at least about 50% pure as measured by HPLC.

COBA can be prepared by reacting OBA with cyclohexanone and a base able to form a carbanion; and recovering the obtained COBA. Optionally, a protected derivative of OBA can be used as a starting material, to obtain PCOBA.

Usually, the reaction is done in the presence of a solvent. Preferably, the solvent is as described above. More preferably, the solvent is THF.

Initially, OBA or POBA is combined with the solvent to obtain a mixture. Then a base able to form a carbanion is added, providing a new mixture.

Preferably, the base is able to form a carbanion. More preferably, the base is LDA; or alkali metal or alkaline earth metal (such as lithium) diisopropylamide; or BuLi. The base may also be Sodium hydride (NaH); or alkali metal or alkaline earth metal (such as sodium or potassium or lithium) salts of bis trimethylsilylamide {MN(SiMe₃)₂}; or metal salt of tert-butoxide (MOtBu)

The reaction of the base with the reagent is exothermic. Preferably, the base is added at a temperature of about 80° C. to about 25° C. For example, when the base is LDA, the addition can be done at ambient temperature, and when the base is BuLi, the addition can be done at a temperature of about −80° C.

Usually, the base is added dropwise. Preferably, the dropwise addition is done during a period of time of about 30 minutes. The new mixture is then stirred. Preferably, the stirring is for about 10 minutes to about 2 hours. More preferably, the new mixture is stirred for about 30 minutes.

Cyclohexanone is then added to the mixture. Preferably cyclohexanone is added dropwise, more preferably, during a period of time of 30 minutes.

Preferably, the obtained mixture is maintained, while being stirred, for about 30 minutes to about 24 hours, more preferably, the stirring is done overnight.

The reaction mixture can then be quenched, by reacting the reaction mixture with a proton donor, such as NH₄Cl. The recovery provides COBA or PCOBA, depending on the starting material.

PCOBA and COBA can then be recovered. Preferably, the recovery stage includes: separating the layers obtained after quenching, washing the organic layer obtained after quenching with brine, and further evaporating the residual organic solvent under reduced pressure (pressure of less than one atmosphere) to obtain COBA or PCOBA.

In another embodiment, the present invention encompasses a hydroxyl protected cyclohexylOBA (PCOBA). Preferably, PCOBA is TBDMS-protected COBA.

The process for preparing COBA or PCOBA can further comprise a process for converting COBA or PCOBA to ODV. COBA and PCOBA can be converted to ODV by reacting COBA or PCOBA with a reducing agent, and recovering to obtain ODV.

Usually, COBA or PCOBA are combined with a solvent to obtain a solution. Solvents that are inert to the reducing agent can be used. Preferably the solvent is THF. Subsequently, a reducing agent is added, preferably, the reducing agent is a metal hydride complex. More preferably, the metal hydride complex is selected from a group consisting of BH₃ derivatives or aluminum hydride derivatives. Most preferably, the reducing agent is LiAlH₄, NaBH₄, NaBH3CN: sodium cyanoborohydride Instead of using metal hydride complex, the hydrogenation may be performed under H₂ pressure in presence of catalyst such Ni or Co.

Usually, the reducing agent is added dropwise to avoid heat accumulation. The addition can be done during a period of time of about 30 min. The addition can preferably be done at a temperature of about −50° C. to about RT. Preferably, the temperature is ambient temperature.

The addition of the reducing agent provides a mixture. Preferably, the mixture is stirred for about 1 hour to about 24 hours. More preferably, the stirring is stirred for over night.

Preferably, the recovery of ODV is done by quenching. More preferably the quenching is done by acidification of the mixture. Acidification is done for example by adding aqueous solution of HCl or NH₄Cl. The quenching, typically, provides a two-phase system, comprising of an aqueous phase and of an organic phase. The phases are separated, and the aqueous phase is neutralized preferably, by adding a base. The neutralization is done by adding a base such as an alkali or alkaline earth metal carbonate/bicarbonate. Preferably, the base is a saturated solution of NaHCO₃.

The process for preparing ODV can further comprise a recovery process. The recovery can be done by extracting ODV from the aqueous layer, such as by adding a water immiscible organic solvent. Preferably, the water immiscible organic solvent is CH₂Cl₂, EtOAc, hexanes or toluene

The extract may then be dried, filtered and evaporated under reduced pressure (pressure of less than one atmosphere). The drying is preferably over Na₂SO₄.

One of ordinary skill of art would appreciate that each above described process can be combined into one continuous process for synthesis of ODV. In such process ODV can be synthesized by combining OBCarboxy, a catalyst and an acid activating agent to obtain an activated acid; recovering the activated acid, combining it with an amine to obtain OBA; reacting the obtained OBA with cyclohexanone and a base able to form a carbanion; recovering the obtained COBA; reacting the obtained COBA, and a reducing agent; and recovering the obtained ODV. Optionally, a protected derivative of OBA (POBA) can be used as a starting material for the process for preparing PCOBA, and wherein, optionally, a protected derivative of COBA (PCOBA) can be used as a starting material for the preparation of ODV.

Having described the invention with reference to certain preferred embodiments, other embodiments will become apparent to one skilled in the art from consideration of the specification. The invention is further defined by reference to the following examples describing in detail the synthesis of the compound OBA, COBA, their protected forms and further their conversion to O-desmethylvenlafaxine. It will be apparent to those skilled in the art that many modifications, both to materials and methods, may be practiced without departing from the scope of the invention.

EXAMPLES Preparation of OBA Example 1

A 500 ml three-neck flask equipped with nitrogen inlet, thermometer and mechanical stirrer was charged with OBcarboxy (10 g, 65.72 mmol), DMF (1 ml) and CH₂Cl₂ (50 ml). The reaction mixture was stirred at 0° C. and SOCl₂ was added dropwise.

The reaction was stirred at ambient temperature for 2 hours and then the solvent was evaporated under reduced pressure. The residue was dissolved in CH₂Cl₂ (50 ml) and dimethylamine-HCl (100 g, 1.22 mol) was added. Then diisopropylethylamine (150 ml, 0.882 mol) was added dropwise. The mixture was stirred at ambient temperature overnight and then washed with a saturated solution of NaHCO₃; a precipitate appeared. The precipitate was filtered under reduced pressure and washed with methylene chloride. The solid so-obtained was dried in a vacuum oven at room temperature to get 5.55 g of OBA (purity 99.45%).

The organic layer was washed with brine and evaporated to dryness yielding crystals 5.84 g OBA (purity 96.57%). Total yield=97.85%.

Preparation of Protected OBA (POBA) Example 2

A 100 ml three-neck flask equipped with nitrogen inlet, thermometer and mechanical stirrer was charged with OBA (2.4 g, 13.39 mmol) TBDMS-Cl (4.5 g, 29.9 mmol), imidazole (5.5 g, 80.78 mmol) and CH₂Cl₂ (20 ml). The reaction mixture was stirred at ambient temperature for 2 hours. The reaction was quenched with brine and a 10% aqueous solution of citric acid The organic phase was then washed with brine and dried over Na₂SO₄. After filtration the solvent was evaporated under reduced pressure to get 3.82 g OBA-P (purity: 99.34%, yield: 97.45%).

Example 3

In a 50 ml flask equipped with a mechanical stirrer, OBA (1.45 g, 8.09 mmol) was dissolved at room temperature in DHP (8 ml) under nitrogen. Pyridinium p-toluene sulfonate (PPTS, catalytic amount) was added and the reaction mixture was heated to 55° C. for 5 hours. The reaction was monitored by HPLC. EtOAc was added and the organic layer was washed with brine, dried over MgSO₄ and filtered under reduced pressure to get OBA-DHP.

Preparation of Protected COBA (PCOBA) Example 4

A 100 ml three-neck flask equipped with nitrogen inlet, thermometer and mechanical stirrer was charged with OBA-TBDMS (3.8 g 12.95 mmol) and THF (50 ml). The solution was cooled to −80° C. and n-BuLi (1M in Hexane 8.5 ml 13.6 mmol) was added dropwise. The reaction was stirred at −80° C. for 45 min and cyclohexanone (1.7 g, 17.32 mmol) was added dropwise. This mixture was stirred for 3 hours at this temperature and poured into a saturated solution of NH₄Cl. The layers were separated.

The organic layer was washed with brine and dried over Na₂SO₄. After filtration the solvent was evaporated under reduced pressure to get 4.85 g of COBA-P (purity: 79.63%, yield: 95.65%)

Preparation of COBA Via OBA Example 5

A 100 ml three-neck flask equipped with nitrogen inlet, thermometer and mechanical stirrer was charged with OBA (1.2 g, 6.69 mmol) and THF (10 ml). The mixture was stirred at ambient temperature and LDA (2M in THF 7 ml, 14.02 mmol) was added dropwise. The mixture was stirred at this temperature for 30 min and cyclohexanone (1.4 g, 14.26 mmol) was added dropwise. This mixture was stirred overnight at ambient temperature and then poured into a NH₄Cl aqueous saturated solution. The layers were separated and the organic phase was washed with brine dried over Na₂SO₄ and evaporated under reduced pressure to get COBA.

Preparation of ODV Via PCOBA Example 6

A 100 ml three-neck flask equipped with nitrogen inlet, thermometer and mechanical stirrer was charged with PCOBA-TBDMS (2.2 g, 5.6 mmol) and THF (30 ml). This solution was stirred at ambient temperature and LiAlH₄ (1M in THF10 ml, 10 mmol) was added dropwise. The mixture was stirred at ambient temperature overnight. This mixture was then acidified with a 10% aqueous solution of HCl. The layers were separated and the aqueous phase was basified with a NaHCO₃ saturated solution. The aqueous layer was extracted with CH₂Cl₂, dried over Na₂SO₄, filtered and evaporated under reduced pressure to get 0.43 g of ODV (purity=100%).

Preparation of ODV Via COBA Example 7

A 100 ml three-neck flask equipped with nitrogen inlet, thermometer and mechanical stirrer is charged with COBA-TBDMS (2.2 g, 5.6 mmol) and THF (30 ml). This solution is stirred at ambient temperature and LiAlH₄ (1M in THF10 ml, 10 mmol) is added dropwise. The mixture is stirred at ambient temperature overnight. This mixture is then acidified with a 10% aqueous solution of HCl. The layers are separated and the aqueous phase is basified with a NaHCO₃ saturated solution. The aqueous layer is extracted with CH₂Cl₂, dried over Na₂SO₄, filtered and evaporated under reduced pressure to obtain ODV. 

1. 2-(4-hydroxyphenyl)-N,N-dimethylacetamide having the structure:

2-3. (canceled)
 4. A process for preparing the 2-(4-hydroxyphenyl)-N,N-dimethylacetamide of claim 1 comprising forming an acid-activated derivative of 4-hydroxyphenylacetic acid (4-hydroxyphenyl)acetic acid), and reacting the activated acid with dimethylamine.
 5. A process according to claim 4 wherein the acid-activated derivative of 4-hydroxyphenylacetic acid is prepared by combining 4-hydroxyphenylacetic acid with an acid activating agent and a catalyst, and optionally recovering the activated acid.
 6. A process according to claim 4 wherein the activated acid is combined with an amine to obtain OBA, and optionally recovering the OBA.
 7. The process of claim 5, wherein the catalyst is an organic catalyst.
 8. The process of claim 5, wherein the catalyst is dimethyl formamide (DMF) or Pyridinium p-toluene sulfonate (PPTS).
 9. The process of claim 4, wherein the acid is activated in the presence of a solvent.
 10. The process of claim 9, wherein the solvent is selected from a group consisting of C₆₋₁₂ aromatic hydrocarbon, a C₁₋₄ halogenated hydrocarbon, a C₄₋₈ ether and mixtures thereof.
 11. The process of claim 9, wherein the solvent is selected from a group consisting of toluene, CH₂Cl₂ and THF.
 12. The process of claim 9, wherein the solvent is CH₂Cl₂.
 13. The process of claim 9, wherein the solvent is cooled to a temperature of about −40° C. to about 70° C.
 14. The process of claim 13, wherein the solvent is cooled to a temperature of about −10° C. to about 10° C.
 15. The process of claim 5, wherein the activating agent is SOCl₂, CoCl₂, DCC(N′-dicyclohexyl carbodiimide) or analogs, HOBT or analogs, or FMOC or analogs.
 16. The process of claim 15, wherein the activating agent is SOCl₂.
 17. The process of claim 5, wherein the activated acid is recovered by removing the solvent.
 18. The process of claim 5, wherein the dimethylamine is a salt, and subsequent to its reaction with the activated acid, a second amine is added.
 19. The process of claim 18, wherein the amine salt is dimethylamine HCl.
 20. The process of claim 19, wherein the second amine is a C₃-C₉ tertiary amine.
 21. The process of claim 20, wherein the second amine is diisopropylamine.
 22. The process of claim 17, wherein recovery is done by quenching; washing, filtering, and drying.
 23. The process of claim 5, further comprising converting OBA to O-desmethylvenlafaxine or a salt thereof.
 24. Protected hydroxyphenyl dimethylamide of the following structure:

wherein x is a hydroxy protecting group. 25-30. (canceled)
 31. A process for preparing compound of claim 24 comprising combining OBA with a suitable hydroxyl protecting agent and optionally a base. 32-39. (canceled)
 40. 2-(1-hydroxycyclohexyl)-2-(4-hydroxyphenyl)-N,N-dimethylacetamide (COBA) having the following structure:


41. (canceled)
 42. A process for preparing the compound of claim 40 comprising reacting OBA with cyclohexanone and a base able to form a carbanion and recovering the obtained COBA. 45-53. (canceled)
 54. Hydroxyl protected 2-(1-hydroxycyclohexyl)-2-(4-hydroxyphenyl)-N,N-dimethylacetamide (PCOBA) having the following structure:

wherein x is a hydroxy protecting group.
 55. (canceled)
 56. A process for preparing the hydroxyl protected 2-(1-hydroxycyclohexyl)-2-(4-hydroxyphenyl)-N,N-dimethylacetamide of claim 54 comprising reacting a hydroxy protected OBA (POBA) with cyclohexanone and a base able to form a carbanion and recovering the obtained PCOBA.
 57. A process for preparing ODV (O-desmethylvenlafaxine) comprising converting the COBA of claim 40 or the PCOBA of claim 54 to ODV or a salt thereof. 58-66. (canceled)
 67. A process for preparing ODV (O-desmethylvenlafaxine) or salts thereof comprising the steps of: combining OBCarboxy, a catalyst and an acid activating agent to obtain an activated acid; recovering the activated acid, combining it with dimethylamine or a salt thereof and an amine to obtain OBA; reacting the obtained OBA with cyclohexanone and a base able to form a carbanion; recovering the obtained COBA; reacting the obtained COBA, and a reducing agent; and recovering the obtained ODV or a salt thereof.
 68. (canceled)
 69. A process for preparing ODV (O-desmethylvenlafaxine) or salts thereof comprising the steps of: (i) preparing OBA from 4-hydroxyphenylacetic acid by a process according to claim 4; (ii) optionally preparing POBA from OBA by a process according to claim 31; (iii) preparing COBA from OBA by a process according to claim 42; (iv) optionally preparing PCOBA from POBA according to claim 56; (v) converting the COBA or PCOBA to ODV by a process according to claim
 57. 70-71. (canceled) 